feat(opts): use style options

style.go

@@ -75,20 +75,34 @@ const (
 // A set of properties.
 type rules map[propKey]interface{}
 
+// StyleOption is a function that applies a style option to a Style.
+type StyleOption func(*Style)
+
+// WithString sets the underlying string value for this style.
+func WithString(strs ...string) StyleOption {
+	return func(s *Style) {
+		s.value = joinString(strs...)
+	}
+}
+
 // NewStyle returns a new, empty Style. While it's syntactic sugar for the
 // Style{} primitive, it's recommended to use this function for creating styles
 // in case the underlying implementation changes. It takes an optional string
 // value to be set as the underlying string value for this style.
-func NewStyle(strs ...string) Style {
-	return renderer.NewStyle(strs...)
+func NewStyle(opts ...StyleOption) Style {
+	return renderer.NewStyle(opts...)
 }
 
 // NewStyle returns a new, empty Style. While it's syntactic sugar for the
 // Style{} primitive, it's recommended to use this function for creating styles
 // in case the underlying implementation changes. It takes an optional string
 // value to be set as the underlying string value for this style.
-func (r *Renderer) NewStyle(strs ...string) Style {
-	return Style{r: r}.SetString(strs...)
+func (r *Renderer) NewStyle(opts ...StyleOption) Style {
+	s := Style{r: r}
+	for _, opt := range opts {
+		opt(&s)
+	}
+	return s
 }
 
 // Style contains a set of rules that comprise a style as a whole.
@@ -98,13 +112,19 @@ type Style struct {
 	value string
 }
 
+// joinString joins a list of strings into a single string separated with a
+// space.
+func joinString(strs ...string) string {
+	return strings.Join(strs, " ")
+}
+
 // SetString sets the underlying string value for this style. To render once
 // the underlying string is set, use the Style.String. This method is
 // a convenience for cases when having a stringer implementation is handy, such
 // as when using fmt.Sprintf. You can also simply define a style and render out
 // strings directly with Style.Render.
 func (s Style) SetString(strs ...string) Style {
-	s.value = strings.Join(strs, " ")
+	s.value = joinString(strs...)
 	return s
 }
 
@@ -173,7 +193,7 @@ func (s Style) Render(strs ...string) string {
 	}
 
 	var (
-		str = strings.Join(strs, " ")
+		str = joinString(strs...)
 
 		te           = s.r.ColorProfile().String()
 		teSpace      = s.r.ColorProfile().String()